A vane compressor includes a cylinder block in which a cylinder chamber having an ellipsoidal inner wall is formed, a rotor that is rotatably supported in the cylinder chamber and rotates by receiving a drive force, and plural vanes that are inserted in plural vane slots formed on an outer circumferential surface of the rotor, respectively. While the rotor rotates, the vanes are protruded by backpressure generated in backpressure spaces in the vane slots, so that end edges of the vanes are slidably contacted with the inner wall of the cylinder chamber and the vanes reciprocate in the vane slots.
Since the backpressure is generated by high-pressure refrigerant in the cylinder chamber in operation, the vanes are protruded from the vane slots and the end edges of the vanes are slidably contacted with the inner wall of the cylinder chamber, so that a volume of the backpressure spaces is kept almost constant.
On the other hand, pressure in the compressor becomes uniform while it is stopped, so that the backpressure to protrude the vanes doesn't act on the vanes. Therefore, a vane oriented vertically upward drops down in a vane slot while ejecting refrigerant and oil in the vane slot out through clearances between inner walls of the vane slot and the vane due to its own weight. Therefore, the volume of the backpressure spaces may gradually decrease if its stopped state continues. When the compressor is started up from this state, the volume of the backpressure spaces is small and a volume of the refrigerant and the oil flowing into the backpressure spaces through the clearances between the inner walls of the vane slot and the vane is small, so that the vane cannot protrude quickly even if a force for protruding the vane acts thereon due to a centrifugal force by the rotation of the rotor. Therefore, the backpressure spaces become negative pressure and the vane is difficult to protrude, so that the end edge of the vane is not sufficiently protruded to the inner wall surface of the cylinder chamber. As a result, the vane is repeatedly contacted-with and hit-back-from the inner wall surface of the cylinder chamber and thereby noises (chattering) may occur.
A Patent Document 1 listed below discloses a compressor that prevents chattering. In the compressor, a support plate is disposed on a bottom of a vane slot and pins are fixed on the support plate. Coil springs for biasing a vane in a protruding direction are inserted to the pins. As a result, the vane does not drop down in the vane slot in a stopped state of the compressor. When the compressor is started up, the vane is protruded from the vane slot by a biasing force of the coil springs and its end edge is slidably contacted with an inner wall of a cylinder chamber, so that chattering is prevented.